Engineers have called it "the hundred-thousand-piece jigsaw," and today it was unveiled as the centerpiece of a new extension to London's Heathrow Terminal 2 building. The aluminum-clad sculpture titled "Slipstream," by artist RIchard Wilson, reaches 78 meters (256 feet) and weighs upward of 77 metric tons (85 tons). Engineering firm Price & Myers was tasked with the job of designing parts for the piece, which twists and turns in simulation of a small airplane as it moves through space performing a series of acrobatic maneuvers.

Algorithms and hand-drawing

Wilson's idea was to replicate the flight path of a stunt plane in a fluid, three-dimensional form. The resulting sculpture is suspended across the atrium-like space of the Terminal hall in a dynamic silver sweep. Processes used to create the tumbling shape of the piece include a computer program that helped to plot the different points of movement of the plane, and then interpolate between the points to come up with a line of movement.

The many surfaces of the final sculpture were calculated by algorithm to maintain the flowing form in aluminum cladding. However, as programming each step in the assembly would have been more time-consuming than hand-drawing, much of the work in delineating the placement of each piece was actually done through hand-sketching.

Not just a shiny surface

The structure makes used of a "stressed skin" which covers a series of pieces made from plywood and oriented strand board (OSB). This means that the skin takes some of the force of weight and transfers it back to the bearing steel structure. The cladding was fixed with visible "rivets," recalling aircraft construction. According to the engineers, "a jumbo jet contains about a million rivets and Slipstream has about half that number."

A work of many parts

Beneath the cladding, a complex series of timber "bulkhead" structures had to be assembled and connected by steel sections attached to the four roof-support columns. The sculpture is mounted like a bridge between each sets of columns. A standard size for each of 23 sections, or "cassettes," used to complete the sculpture was determined by the capacity of a flat-bed lorry.

Describing the process of erecting the sculpture as assembling a giant jigsaw, the engineers explained that each cassette was made up of numerous timber supports and pieces of ply that had to be fit together, with the aluminum cladding covering each section precisely.

Motion studies and terrorism

The engineers point out that the sculpture harkens back to earlier artistic studies in motion, such as those by photographer Eadweard Muybridge in the late 19th century. Though the flight path was created by the artist and designers, a stunt pilot was commissioned to recreate the flight and was able to do so successfully.

Once the form and materials had been decided, the sculpture had to be tested for stability, in particular to determine how it would behave in an explosion, such as in a terrorist attack. A mocked-up section was put through a test explosion to determine whether it would split into dangerous shrapnel. The section proved even more robust than expected and, engineers say, "it stayed pretty well intact."

The Terminal 2 extension was designed by Luis Vidal Architects and will be officially opened as "the Queen's Terminal" by Queen Elizabeth II on June 23.

The sketch shows the flight path delineated by the plane and the sculptural form above (Photo: Heathrow Airports Limited)

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